Exposure to sunlight leads to the development of sunburn, premature aging of the skin, cataracts, immune suppression, and skin cancer. Actinic keratosis (AK) of the skin represents an early stage of a continuum that may ultimately progress to squamous cell carcinoma (SCC). Actinic cheilosis is the labial equivalent of AK. The term actinic cheilitis is often used; however, actinic or solar cheilosis (SC) is more accurate because this sun-induced neoplastic disease is primarily non-inflammatory.1

The highly developed lip vermilion exists only in man and is bounded by the keratinized skin and mucous membrane of the inner labia.2 The epidermis is characterized by a highly developed stratum lucidum and a very thin stratum corneum. Hair and sweat glands are absent but dermal papillae are abundant, leading to the rich vascular supply that imparts the characteristic red color (vermilion). In dark-complected individuals, the red hue is camouflaged by increased melanin deposits.3

SC is a precancerous neoplasia found primarily on the lower lip of light-skinned individuals. Given the high risk for the progression of SC to SCC of the lip vermilion and the high rate of discordance between clinical and histologic findings, a biopsy is indicated in the presence of clinically discernable degenerative changes.1 Prevention, early diagnosis, effective therapeutic intervention, and close long-term follow-up are paramount.